Developing a TaqMan probe to detect, through real- time PCR, Ralstonia solanacearum wich causes moko in Musa spp. in Colombia : [P2-25]

To manage disease, the genetic structure of populations of a given pathogen should be understood and characterized. A tool can then be developed that is sensitive and specific enough to permit the quantification of minimal concentrations of pathogenic cells. Hence, the pathogen can be detected early and strategies for its management implemented. This study therefore aimed to determine the variability of the genetic diversity of a population of #Ralstonia solanacearum# in different regions of Colombia. The bacterium causes bacterial wilt, also known as moko. It was first reported in Colombia during the 1950s as a major disease that severely limits the production of plantain, banana, and heliconia crops (1). We first evaluated 72 #R. solanacearum# strains to determine their variability across infected plantain, banana, and heliconia crops grown in seven departments of Colombia. The strains were first classified phylogenetically, using multiplex PCR (2), which identified them as phylotype II. To determine sequevars, the strains underwent multiplex PCR again and sequence analysis of the endoglucanase gene. The genetic diversity of the 72 strains enabled us to classify 62 strains, isolated from plantain and banana in five departments of Colombia, as phylotype II, sequevar 4 (II/4). For the sixth department (Antioquia), seven strains were identified as belonging to the nonpathogenic II/4 group on banana (NPB), and for the last department (Magdalena), three strains were identified as II/6. We used these results to develop and implement a TagMan® probe that was sensitive and specific enough to quantify minimal concentrations of the bacterium's cells in plants, thus enabling early detection of the pathogen. The probe was then used with real-time PCR (qPCR) to evaluate samples obtained from infected crops of plantain, banana, and heliconia growing in different departments of Colombia. We could detect pathogenic strains from plantain and homologize them, the probe proved specific to #R. solanacearum#, detecting as few as 1 '103 cfu mL-' when amplifying directly from samples of infected tissue. (Résumé d'auteur